Shear strength of mineral filter cakes

Abstract

This study covers the shear strength measurements of very fine pressure filter cakes of TiO 2 , calcite fractions, labosil, kaolin and synthetically prepared glass spheres. The shear strength behavior of all these cakes at the full range of saturation, i.e. from S = 0.0 to S = 1.0, showed the same tendency as in the case of Schubert’s diagram for the tensile strength of the mineral filter cakes. The dependence of the shear strength of the filter cakes on the used pressure, particle size and shape has been analyzed. The effect of a surfactant (Lutensol TO3) treatment on the shear strength of the cakes was also investigated. It has been found from the laboratory scale experiments that the shear strength of all analyzed materials is strongly dependent on the applied filtration pressure: the higher the pressure the greater the shear strength. The shear strength also increases with the decreasing particle size. The shape of the particles has also a very large effect on the shear strength of the cake. The surfactant treatment, on the other hand decreased the shear strength of the cakes very sharply. Although the surfactant helps the filtration operation giving less residual moisture contents in the cakes, it was not possible to obtain saturation degrees higher than 50 and 60 % for kaolin and calcite when using the surfactant.